Slurry explosive comprising ammonium nitrate and aluminum powder

ABSTRACT

A slurry explosive containing, as the main ingredients, (1) 40 to 80 percent by weight of ammonium nitrate or a mixture of ammonium nitrate and an alkali metal nitrate or a mixture of ammonium nitrate and an alkaline earth metal nitrate or a mixture of ammonium nitrate, an alkali metal nitrate and an alkaline earth metal nitrate, (2) 5 to 20 percent by weight of aluminum powder consisting of aluminum powder (a) which is manufactured by the ball milling method or the stamping method, and the particle size of which is 30 mesh (JIS sieve) or below; and aluminum powder (b) having no leafing property which is manufactured by the atomizing method or the graining method, the particle size of which is 30 mesh (JIS sieve) or below, the mixing ratio by weight of aluminum powder (a) and aluminum powder (b) being 50 to 20: 50 to 80, and (3) 5 to 25 percent by weight of water.

States 1 atem [151 3,664,897 Wakazono et al. 5] 23, 1972 54] SLURRY EXPLOSIVE COMPRISING 3,367,805 2/1968 Clay et a1 ..149 114 x AWONIUM NITRATE AND 3,432,371 3/1969 Grant ..l49/43 X ALUWNUM POWDER FOREIGN PATENTS OR APPLICATIONS [72] 898,681 6/1962 Great Britain ..149/43 9 s 1 Nnhama'sh" an of Japan Primary Examiner-Leland A. Sebastian [73] Assignee: Sumitomo Chemical Co., Ltd., Higashi-ki, Attorney-Sughrue, Rothwell, Mion, Zinn & MacPeak Osaka [22] Filed: Oct. 24, 1969 [57] ABS CT A slurry explosive containing, as the main ingredients, (1) 40 [21] Appl' 869324 to 80 percent by weight of ammonium nitrate or a mixture of ammonium nitrate and an alkali metal nitrate or a mixture of [30] Foreign A lication Priority Data ammonium nitrate and an alkaline earth metal nitrate or a mixture of ammonium nitrate, an alkali metal nitrate and an Oct. 31, 1968 Japan ..43/79809 alkaline earth metal nitrate (2) 5 to 20 percent by weight of aluminum powder consisting of aluminum powder (a) which is 521 US. Cl ..i1gs/ g8,11g9/fi9,114499/;1l 14, manufactured by the ball milling method or the stamping Int Cl (506) 4 method, and the particle size of which is 30 mesh (JIS sieve) or below; and aluminum powder (b) having no le afing propep [58] Field ofSearch ..l49/38, 39,41,43, 44, 114 ty which is manufactured by the atomizing method or the [56] References Cited graining method, the particle size of which is 30 mesh (JlS sieve) or below, the mixing ratio by weight of aluminum UNITED STATES PATENTS powder (a) and aluminum powder (b) being 50 to 20: 50 to 8 5 2 3/19 2 B 149/38 x 80, and (3) 5 to 25 percent by weight ofwater. 2,5 9, 3 5 yers 3,307,986 3/1967 Grant ..l49/4l X 12 Claims, No Drawings SLURRY EXPLOSIVE COMPRISING AWONIUM NITRATE AND ALUMINUM POWDER BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slurry explosive containing aluminum powder and having an improved specific gravity and an improved sensitivity.

2. Description of the Prior Art A slurry explosive containing ammonium nitrate, or ammonium nitrate and a nitrate of an alkali metal and/or an alkaline earth metal, especially a slurry explosive containing ammonium nitrate and 2,4,6-trinitrotoluene (hereinafter referred to as TNT) or aluminum powder or a mixture thereof and water as the main ingredients is known as an effective industrial explosive, and has been satisfactorily used at sites such as hard rock or water springs, where an ammonium nitrate-fuel oil explosive cannot be employed. Such an explosive is absolutely safe in handling, and can easily be charged into a bore hole. Therefore, in recent years, such an explosive has been charged by means of a forcing pump utilizing the slurry characteristic thereof. Such a slurry explosive has a higher explosion velocity and illustrates a better explosive performance in comparison with the well known ammonium nitrate-fuel oil explosive.

Accordingly, such a slurry explosive is effective in boulder blasting, and crushing costs in succeeding steps are considerably reduced. In addition, such a slurry explosive is lower in transportation cost and boring cost, since it is higher in specific gravity than the ammonium nitrate-fuel oil explosive.

Furthermore, such a slurry explosive is not only excellent in explosive performance but is also characterized by being safer because water is contained in the composition.

Among the slurry explosive compositions used today, there are the following system compositions: ammonium nitrate TNT water, ammonium nitrate-TNT-aluminum-water, ammonium nitrate-smokeless powder-water, ammonium nitratesmokeless powder-aluminum-water, ammonium nitrate-aluminum-water and ammonium nitrate-fuel-water. On considering explosive performance and cost, the ammonium nitrate- TNT-water or ammonium nitrate-aluminum-water system is most effectively used.

Aluminum used for the preparation of slurry explosives has been conventionally selected from the classes in a limited range, such as ball milling aluminum powder. Such aluminum powders are occasionally employed by coating the surface thereof with stearic acid, as described in the specification of US. Pat. No. 3,367,805. This is due because the aluminum powder must coexist with water in the slurry explosive. Consequently, this causes the cost of manufacturing slurry explosives to be high. In addition, such aluminum powder, for example that manufactured by the ball milling method or the stamping method, has a very small bulk specific gravity, and therefore the specific gravity of a slurry explosive containing such an aluminum powder is often 1.1 to 1.2.

This not only makes the transportation cost thereof high, but also interrupts complete charging into a bore hole filled with water because of incomplete sedimentation.

Aluminum powder manufactured by the ball milling method or the stamping method is of very high sensitivity. For example, it is recognized that when a slurry explosive consisting of 72 percent by weight ammonium nitrate, 7 percent by weight aluminum powder manufactured by the ball milling method, 20 percent by weight water, and 1 percent by weight carboxymethyl cellulose (hereinafter referred to as CMC) is charged in a steel pipe (35 mm. inner diameter and 250 mm. in length) initiation takes place with only one No. 6 electric cap. Such an explosive can never be a safe explosive, and it is very difficult to flow charge such an explosive by means of a pump. However, the high sensitivity of aluminum powder manufactured by the ball milling method or the stamping method is never a defect, because with the TNT system slurry explosive of low sensitivity, it is necessary to use a very high cost, strong booster. For example, in the specification of U.S. Pat. No. 3,097,l2l, the use of bentonite is recommended for initiating a TNT system slurry explosive. According to research of the present inventors, in experiments to determine the explosive velocity of a TNT system slurry explosive by the Dautriche method using a 35 mm. steel pipe, the following results (shown in Table l) were obtained.

It is often found that the kind and amount of booster used has a great influence on explosion velocity.

A TNT-aluminum system slurry explosive solves the above problems of the TNT-slurry explosives. The TNT-aluminum system slurry explosive has the merit of the high sensitivity of aluminum powder manufactured by the ball milling method or the stamping method and the high specific gravity and high explosive power of TNT, and offers an extremely high performance. However, this explosive is high in cost and also is very poor from a safety viewpoint. In addition, this explosive has a problem with production control because two kinds of very different dangerous materials, such as TNT and aluminum powder are required in its manufacture.

SUMMARY OF THE INVENTION In an ammonium nitrate-aluminum powder-water slurry explosive, an improved explosive is obtained when the aluminum powder consists of aluminum powder (a) which is manufactured by the ball milling method or the stamping method, the particle size of which is 30 mesh (JIS sieve) or below, and aluminum powder (b) having no leafing property which is manufactured by the atomizing method or the graining method, the particle size of which is 30 mesh (JIS sieve) or below, the mixing ratio by weight of the aluminum powder (a) and the aluminum powder (b) being about 50 to 20 50 to 80.

Percentages and other materials which can partially replace ammonium nitrate are disclosed in the specification.

One object of the invention is to provide an aluminum-containing slurry explosive having a specific gravity comparable to that of the TNT system slurry explosive.

A further object is to provide a safe explosive with an initiating sensitivity which can be freely controlled.

Another object is to provide an explosive which is highly economical.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The above objects are accomplished by providing a slurry explosive containing as the main ingredients: (1 40 to percent, by weight, of ammonium nitrate or a mixture of ammonium nitrate and an alkali metal nitrate or a mixture of ammonium nitrate, and an alkaline earth metal nitrate or a mixture of ammonium nitrate, an alkali metal nitrate and alkaline earth metal nitrate; (2) 5 to 20 percent by weight of aluminum powder consisting of aluminum powder (a) which is manufactured by the ball milling method or the stamping method Aluminum" 445, 22 (1967)), the particle size of which is 30 mesh (JIS sieve) or below, and aluminum powder (b) having no leafing property which is manufactured by the atomizing method or the graining method and the particle size of which is 30 mesh (JIS sieve) or below, the mixing ratio, by weight, of

aluminum powder (a) and aluminum powder (b) being 50 to 20 50 to 80; and (3) to 25 percent, by weight, of water. The slurry explosive of the present invention may contain one or more materials such as TNT, smokeless powder, carbonaceous fuels including carbon powder and fuel oils, etc., and/or a paste for suspension stability, in addition to the above main ingredients.

There is a great difference between aluminum powder (a) manufactured by the ball milling method or the stamping method and aluminum powder (b) manufactured by the uuimizing method or the graining method. The former has a lcuflng property, while the latter does not. Furthermore, aluminum powder (a) is lower in apparent specific gravity and higher in specific surface area and sensitivity in comparison with aluminum powder (b). Therefore, when blending such aluminum powders in various ratios and incorporating the blended aluminum powders into the slurry explosive, a slurry explosive having the desired specific gravity, sensitivity and explosion velocity is obtained. in particular, the aluminum system slurry explosive containing ammonium nitrate, aluminum powder manufactured by the stamping method, aluminum powder manufactured by the atomizing method and water as its main ingredients is most preferably employed because of the facts that its specific gravity is good, its explosion velocity is high, its preparation is easy, and it is safe to use.

Thus, considering the specific gravity, sensitivity and explosion velocity of the slurry explosive when aluminum powder (a) and aluminum powder (b) are incorporated into the slurry explosive in such a ratio that the former is 50 to 20 percent by weight and the latter is 50 to 80 percent by weight, a preferred result is obtained. it is preferred that the amount of these aluminum powders be larger in the economically acceptable range. However, as in apparent from the description at page 4 of the lecture summaries, 1966 Association, Industrial Powder Association Japan, the increase of explosion velocity with the increase in the aluminum content reaches a saturation at an aluminum content of 10 percent by weight, and aluminum powder (b) is extremely low in sensitivity. Therefore in general 5 to 20 percent by weight of aluminum powder is effectively used. The particle size of the aluminum incorporated into the slurry explosive is related to the viscosity of the slurry explosive. That is, in order to suspend aluminum powder having a large particle size, a large amount of paste is required, and therefore, a slurry explosive containing such aluminum powder suffers from deteriorated flowability and lowered sensitivity.

Accordingly, it is preferred that aluminum powder having a lower particle size, preferably mesh or below, be employed.

The results of Dautriche method measurements on the explosion velocity of slurry explosives of the compositions shown in Table 2 are given in Table 3.

TABLE 3 Composition of slurry explosive (percent by weight) Inner diameter Aluminum Aluminum 01' iron powder powder pipe filled by the by the Amwith Filling Explosion atomizing stomping monium explosive density velocity method method nitrate Water Guargum CMC (mm.) (gJemfi) (m./s( C.)

0 72. 1 20 '0. 1 0. 5 80 1. 3, 180 2 67. 1 20 (l. 4 0. 5 35 1. 38 -l, 720 0 72. 1 20 (J. 4 0. 5 35 1. 34 1 71. 1 2O 0. 4 0. 5 35 1. 33 2 70. 1 20 0. 1 0. 5 35 1. 31 3, 820 3 (ii 1 20 O. 4 0. 5 35 1. 30 4. 680 5 74. 1 20 (l. 4 0. 5 35 1. 21 4,100

1 Incomplete explosion.

For example, according to results of experiments by the The measurement was carried out by Dautriche method acpresent inventors, the specific gravities of the explosive amcording to JIS, 10 g. of tertyl was used as a booster, and a No.

monium nitrate-aluminum-water system having incorporated therewith aluminum powder manufactured by the stamping method and aluminum powder manufactured by the atomizing method, in various ratios, are as shown in Table 2.

TABLE 2 6 electric cap was used as the initiator.

As will be understood from these test results, a slurry explosive containing 7 percent by weight of atomizing method aluminum powder exploded incompletely in a 35 mm. inner Composition of slurry explosive, percent by weight Aluminum Aluminum powder by powder by Filling atomizing stamping Ammonium Guardensity, method method nitrate Water gum CMC g./cm.

Since the specific gravity of TNT system slurry explosive is generally 1.30 to 1.35, considering only the specific gravity of the slurry explosive, the content of aluminum powder manufactured by the atomizing method is preferably above 7 perdiameter iron pipe, but exploded completely in 80 mm. thereof. The explosive containing stamping method aluminum powder was recognized to completely explode in 35 mm., even if its aluminum powder content was 5 percent by weight.

cent, by weight. In the case of incorporating above 15 percent, Thus, a slurry explosive containing aluminum (a) and aluby weight, aluminum powder manufactured by the stamping method, the specific gravity of the slurry explosive lowers to an extreme degree and comes close to the specific gravity of water, and therefore the use of the slurry explosive in a water pit is made difficult.

minum (b) in the weight ratio of 2:7, or the like, may be effectively employed in view of specific gravity, sensitivity, explosion velocity and safety in handling.

The present invention will be illustrated with the following examples, which are, however, not to limit the scope of the present invention. The explosion velocity of the slurry explosive having the above composition was 5570 m/sec.

EXAMPLE 1 The initiating sensitivity and explosion velocity of a slurry EXAMPLE 4 explosive containing 7 percent by weight of aluminum powder 5 (average particle size 44 manufactured by the atomizing method and 0 to 3 percent by weight of aluminum powder (by welsh) (average particle size 74 4) manufactured by the stamping g ifia g g g method and having the compositions shown in Table 4 were Aluminum prepared by the ball milling measured. The results are shown in Table 5. method g Particle Size) 1 3 TABLE 4 Composition of slurry explosive (percent, by weight) Aluminum by atom- Aluminum Ainmo- Antimonyl izing by stamping nium potassium Sample method method nitrate Water Guaigum Borax tartai'ate 7 0 72. 5 0. 3 O. l O. 7 1 7l. 5 20 0. 3 0. l 0. l 7 2 70. 5 20 0. 3 0. 1 0. 1 7 3 69. 5 2O 0. 3 0. 1 0. l

TAB LE 5 Aluminum prepared by the atomizing method Initiation by it blasting cap using Initiation by a sg Pamela Sue) 3 (.etryl as a booster blasting cap only Hexamethylene ten e 6 Explosion Explosion cuafgum Filling velocity Filling velocity Antimonyl potassium tartarate 0.1 Sample Tetryl (g). density (m/sec) density (m./sec.)

15 l. 34 15 1. 32 15 1. 30 3, 840 1. 32 10 1.28 4, 670 1. 29 4, 400 The ex losion veloci of the slurr ex losive havin the P y P g Incomplete explosion. above compositions was 5,570 m/sec. at a filling density of 35 A No. 6 electric cap was used for initiation. With 30 percent EXAMPLE 5 by weight of aluminum powder manufactured by the stamping method as the aluminum content, initiation was possible with bore holes having a 3 mch dlanieter and a 6 depth one blasting cap, while, with 22 percent by weight of that alw were made to the bench-cut of andesite at 1.8 m. intervals, minum, initiation was possible by boosting with 15 g. of tetryl, and ofleast resstance f" but was impossible with only a blasting cap. And the sample c, g? kllqgrams of the slurry eXpl sWe havmg the Same in which the total aluminum content was occupied by alu- P? as Example was fined the bore holes' AS ininum powder formed by the stamping method illustrated a the mmatory a 6 ele'ctnc p was employed, and 33 l 4,250 m/sec. explosion velocity. booster, 375 g. of dynamite (grade: SHIN KIRl (nitroglycerin gel type dynamite was employed. EXAMPLE 2 The position of initiation was at the bottom of the hole for two bore holes, at the center thereof for two other bore holes,

and at the upper side thereof for the last two bore holes. After (by weight) explosion, 288 in (about 1,100 ton) of andesite was quarried. To further exemplify material which will describe the alu- Ammonium nitrate Aluminum PDwde by the ban mining meflmd minums used in this invention, all of which are known to the flffii gjfififgfi fgg method 3 art, reference should be made to the following two citations: (average particle size 44,) 7 Aluminum" edited by Kent R. Van Ham, American Society water 20 for Metals, Park, Ohio (1967), Volume I, pages 337-344,

3322 2 tetmmme 3 Volume 2, pages 623-630.

Antimony] potassium tartarate 0.1 what we Claim is:

1. A slurry explosive containing as the main ingredients l) 40 to 80 percent by weight of ammonium nitrate or a mixture of armnonium nitrate and an alkali metal nitrate or a mixture of ammonium nitrate and an alkaline earth metal nitrate or a mixture of ammonium nitrate, an alkali metal nitrate and an alkaline earth metal nitrate, (2) 5 to 20 percent by weight of EXAMPLE 3 aluminum powder consisting of aluminum powder (a) which is manufactured by the ball milling method or the stamping method, the particle size of which is 30 mesh (JlS sieve) or (by weight) below, and aluminum powder (b) having no leafing property 48.0 which is manufactured by the atomizing method or the grain- The slurry explosive composition having the above composition had a 1.29 filling density and a 4,700 m/sec. explosion velocity. In this case, initiation by a blasting cap was possible.

Ammonium nitrate ig f "mate Lh ing method, the particle size of which is 30 mesh (JIS sieve) or F321;; 232 322 23 1? mmmg me 0d 40 below, the mixing ratio by weight of the aluminum powder (a) Aluminum powder by th atomizing method and the aluminum powder (b) being about 50 to 20 50 to 80,

(average Panic!e Size M 7.0 and (3) 5 to 25 percent by weight of water.

water 19 0 2. A slurry explosive according to claim 1, wherein the slur- Carbon powder 5.0

CMC Q9 ry explosive further contains a member selected from the Octadecyltrimethyl ammonium chloride 0 1 group consisting of 2,4,6-trinitrotoluene, smokeless powder,

carbonaceous fuels, and mixtures thereof.

3. A slurry explosive according to claim 1 wherein the slurry explosive further contains a paste for suspension stability.

4. A slurry explosive according to claim 1 wherein aluminum (a) is manufactured by the ball milling method.

5. A slurry explosive according to claim 1 wherein aluminum (a) is manufactured by the stamping method.

6. A slurry explosive according to claim 1 wherein aluminum (b) is manufactured by the atomizing method.

7. A slurry explosive according to claim 1 wherein aluminum (b) is manufactured by the graining method.

8. A slurry explosive according to claim 1 wherein aluminum (a) is lower in apparent specific gravity and higher in specific surface area and sensitivity then aluminum (b).

9. A slurry explosive according to claim 1 wherein aluminum (a) is manufactured by the stamping method and aluminum (b) is manufactured by the atomizing method, and the slurry contains above 7 percent by weight of aluminum (b) but not above 15 percent by weight of aluminum (a).

10. A sluny explosive according to claim 1 containing 40 to 80 percent by weight of ammonium nitrate.

1 l. A slurry explosive according to claim 1 containing 40 to 80 percent by weight of a mixture of ammonium nitrate and an alkali metal nitrate.

12. A slurry explosive according to claim 1 containing 40 to 80 percent by weight of a mixture of ammonium nitrate, an alkali metal nitrate and an alkaline earth metal nitrate. 

2. A slurry explosive according to claim 1, wherein the slurry explosive further contains a member selected from the group consisting of 2,4,6-trinitrotoluene, smokeless powder, carbonaceous fuels, and mixtures thereof.
 3. A slurry explosive according to claim 1 wherein the slurry explosive further contains a paste for suspension stability.
 4. A slurry explosive according to claim 1 wherein aluminum (a) is manufactured by the ball milling method.
 5. A slurry expLosive according to claim 1 wherein aluminum (a) is manufactured by the stamping method.
 6. A slurry explosive according to claim 1 wherein aluminum (b) is manufactured by the atomizing method.
 7. A slurry explosive according to claim 1 wherein aluminum (b) is manufactured by the graining method.
 8. A slurry explosive according to claim 1 wherein aluminum (a) is lower in apparent specific gravity and higher in specific surface area and sensitivity then aluminum (b).
 9. A slurry explosive according to claim 1 wherein aluminum (a) is manufactured by the stamping method and aluminum (b) is manufactured by the atomizing method, and the slurry contains above 7 percent by weight of aluminum (b) but not above 15 percent by weight of aluminum (a).
 10. A slurry explosive according to claim 1 containing 40 to 80 percent by weight of ammonium nitrate.
 11. A slurry explosive according to claim 1 containing 40 to 80 percent by weight of a mixture of ammonium nitrate and an alkali metal nitrate.
 12. A slurry explosive according to claim 1 containing 40 to 80 percent by weight of a mixture of ammonium nitrate, an alkali metal nitrate and an alkaline earth metal nitrate. 